1. Field of the Invention
The present invention relates to a thin film magnetic head comprising at least an inductive magnetic transducer for recording, a method of manufacturing the same, and a magnetic recording apparatus such as, for example, a hard disk drive which comprises the thin film magnetic head.
2. Description of the Related Art
In recent years, an improvement in performance of thin film magnetic heads has been sought in accordance with an increase in the areal density of a magnetic recording medium (hereinafter simply referred to as “recording medium”) such as, for example, a hard disk. As magnetic recording systems applicable to thin film magnetic heads, for example, a longitudinal recording system that a signal magnetic field is oriented in an in-plane direction of a recording medium (a longitudinal direction) and a perpendicular recording system that the signal magnetic field is oriented in a direction perpendicular to the recording medium are well-known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, the perpendicular recording system instead of the longitudinal recording system holds promise for future, because the perpendicular recording system can obtain an advantage that higher liner recording density can be achieved, and a recording medium in which data has been already recorded has resistance to thermal decay effects.
As recording modes using the perpendicular recording system, for example, (1) a mode of using a head (ring type head) facing each other with a gap in between on a side of an end and being magnetically coupled to each other on a side of the other end and a single-layer recording medium and (2) a mode of using a head (single pole type head) being disposed perpendicular to a recording medium and a two-layer recording medium have been proposed. In these modes, based upon a point that the mode using a combination of the single pole type head and the two-layer recording medium has superior resistance to thermal decay, the mode becomes a focus of attention as a mode which can improve the performance of thin film magnetic heads.
In order to improve the recording performance of a perpendicular recording system thin film magnetic head, for example, the following two points are mainly important, when a “main pole layer” which becomes a main flow path of magnetic flux in the single pole type head is designed.
Firstly, in order to increase a recording density, it is required to form a portion with a minute unifrom width (hereinafter referred to as “uniform width portion”), which determines a recording track width of the recording medium, in the main pole layer with high accuracy. Conventionally, the main pole layer is formed through patterning a magnetic layer in a predetermined pattern shape by use of, for example, techniques of photolithography, film formation, etching or the like. When the main pole layer is formed, in order to form the uniform width portion with high accuracy, high processing accuracy is required.
Secondly, in order to prevent magnetic saturation so as to supply a sufficient amount of magnetic flux to the uniform width portion, it is required to bring a portion with a larger width than the uniform width portion (hereinafter referred to as “widening width portion”) in a main pole layer as close to a recording-medium-facing surface (air bearing surface) as no emission of excessive magnetic flux is induced. The position of a front edge (an edge on a side close to the air bearing surface) of the widening width portion determines a position where the width of the main pole layer expands from the uniform width portion to the widening width portion, and the position is generally called a “flare point”. The flare point is a position where the magnetic flux flowing through the main pole layer from the widening width portion to the uniform width portion is focused, so from the viewpoint of supplying the magnetic flux to the uniform width portion, the flare point is one of factors which determine the recording performance of the thin film magnetic head.
However, conventional methods of manufacturing a thin film magnetic head has such a problem that in spite of the fact that highly accurate formation of the uniform width portion and proper positioning of a flare point are required in order to improve the recording performance, it is difficult for them to be compatible. The reason why it is difficult is as follows.
In the case where a photoresist is selectively exposed by use of, for example, photolithography so as to form a photoresist pattern which is required to form the main pole, when a region with a minute width corresponding to the uniform width portion and a region with a wide width corresponding to the widening width portion are included in the photoresist pattern to be exposed, a surrounding portion of the region with the minute width is unnecessarily exposed by an influence of reflected light generated during exposure, so that an exposed region may be expanded. When the exposed region is expanded, the forming accuracy of the photoresist pattern declines, so it is difficult to form the uniform width portion with high accuracy. Further, as the flare point comes closer to the air bearing surface, thereby a ratio of the region with the wide width to the region with the minute width increases, a problem with the forming accuracy of the uniform width portion becomes more pronounced. Therefore, conventionally, the highly accurate formation of the uniform width portion and proper positioning of the flare point have a trade-off relationship therebetween. In order to prove the practicality and promise of the perpendicular recording system, and spread high-capacity hard disk drives using the system, there is an urgent need to overcome the above problem and achieve the improvement in the recording performance.
In addition, for example, a related art of which an object is to improve the recording performance of a thin film magnetic head using the perpendicular recording system like the present invention has been disclosed by Takahashi et al. in Japanese Unexamined Patent Application Publication No. Hei 6-274811. Takahashi et al. have disclosed a technique to achieve high-density recording through using an appropriate material of a perpendicular magnetic head. However, no specific way to achieve the compatibility between the highly accurate formation of the main pole layer and proper positioning of the flare point has been indicated in the related art.